PANCREAS -

It is derived from the endoderm of the embryo.

Structure. The pancreas lies inferior to the stomach in a bend of the duodenum.

• It is both an exocrine and an endocrine gland i.e. heterocrine gland.
• A large pancreatic duct runs through the gland, carrying enzymes and other exocrine digestive secretions from the pancreatic acinar cells to the small intestine. The tissue of the pancreas has in addition to the acinar cells, groups of cells called islets of Langerhans, after the name of their discoverer (1869), which produce endocrine secretions.
• Four kinds of cells have been identified in the islets.

(i) Alpha cells (about 20%) produce glucagon. Alpha cells are also called A-cells. (ii) Beta cells (about 70%) produce insulin. Beta cells are also called B-cells.

(iii) Delta cells or D-cells (about 5%) produce somatostatin (SS). (iv) PP cells or F-cells (5%), produce pancreatic polypeptide (PP).

• Beta cells are usually found towards the middle of the islet, the alpha cells towards the periphery of the islet and Delta (D) and F-cells are found scattered.